Abstract

Soy products contain isoflavones (genistein, daidzein, and
glycitein) that display biological effects when ingested by
humans and animals, these effects are species, dose and age
dependent. Therefore, the content and quality of isoflavones in
soybeans is a key to their biological effect. Our objective was
to identify loci that underlie isoflavone content in soybean
seeds. The study involved 100 recombinant inbred lines (RIL) from
the cross of ‘Essex’ by ‘Forrest,’ two cultivars that contrast
for isoflavone content. Isoflavone content of seeds from each RIL
was determined by high performance liquid chromatography (HPLC).
The distribution of isoflavone content was continuous and
unimodal. The heritability estimates on a line mean basis were
79% for daidzein, 22% for genistein, and 88% for glycitein.
Isoflavone content of soybean seeds was compared against 150
polymorphic DNA markers in a one-way analysis of variance. Four
genomic regions were found to be significantly associated with
the isoflavone content of soybean seeds across both locations and
years. Molecular linkage group B1 contained a major QTL
underlying glycitein content (P=0.0001,R2=50.2%), linkage
group N
contained a QTL for glycitein (P=0.0033,R2=11.1%)
and a QTL for daidzein (P=0.0023,R2=10.3%) and linkage
group A1 contained a QTL for daidzein (P=0.0081,R2=9.6%).
Selection for these chromosomal regions in a marker assisted
selection program will allow for the manipulation of amounts and
profiles of isoflavones (genistein, daidzein, and glycitein)
content of soybean seeds. In addition, tightly linked markers can
be used in map based cloning of genes associated with
isoflavone content.